I'd agree with SuicideJunkie.  Also, I'm a bit surprised that disk IO appears to be the culprit here. Normally, the OS should buffer/cache read files in RAM (if there is enough free RAM) for the very purpose of being able to access them faster subsequently.

You might also try telling the respective filesystem to not update inode access times (mount option noatime) — unless it's already set up that way, of course. I've found that this can provide quite a performance boost.